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Abstract:

The present invention relates to a magnesium-based composite material
includes at least two magnesium-based metallic layers; and at least one
magnesium-based composite layer respectively sandwiched by the at least
two magnesium-based metallic layers. The present invention also relates
to a method for fabricating a magnesium-based composite material, the
method includes the steps of: (a) providing at least two magnesium-based
plates; (b) providing a plurality of nanoscale reinforcements; (c)
sandwiching the nanoscale reinforcements between the at least two
magnesium-based plates to form a preform; and (d) hot pressing the
preform to achieve the magnesium-based composite material.

3. The magnesium-based composite material as claimed in claim 2, wherein
the material of the nanoscale reinforcements is selected from a group
consisting of carbon nanotubes, carbon nanofibers, silicon carbide
nano-particles, alumina nano-particles, titanium carbide nano-particles,
and any combination thereof.

4. The magnesium-based composite material as claimed in claim 2, wherein a
weight percentage of the nanoscale reinforcements in the magnesium-based
composite material is in the approximate range from 0.5% to 2%.

5. The magnesium-based composite material as claimed in claim 2, wherein a
diameter of the nanoscale reinforcements is in the approximate range from
1 nanometer to 100 nanometers.

6. The magnesium-based composite material as claimed in claim 2, wherein
the material of the matrix is pure magnesium or magnesium alloy.

7. The magnesium-based composite material as claimed in claim 6, wherein
the components of the magnesium alloy comprises magnesium and other
elements selected from a group consisting of zinc, manganese, aluminum,
thorium, lithium, silver, calcium, and any combination thereof.

8. The magnesium-based composite material as claimed in claim 7, wherein a
weight ratio of the magnesium to the other elements is more than about
4:1.

9. A method for fabricating a magnesium-based composite material, the
method comprising the steps of:(a) providing at least two magnesium-based
plates;(b) providing a plurality of nanoscale reinforcements;(c)
sandwiching the nanoscale reinforcements between the at least two
magnesium-based plates to form a preform; and(d) hot pressing the preform
to achieve the magnesium-based composite material.

10. The method as claimed in claim 9, wherein step (c) further comprises
substeps of:(c1) forming a binder film on a surface of one of the two
magnesium-based plates;(c2) uniformly sprinkling the nanoscale
reinforcements on the binder film; and(c3) covering the nanoscale
reinforcements by the other one of the magnesium-based plates to achieve
the preform.

11. The method as claimed in claim 10, wherein the material of the binder
film is adhesive at room temperature and volatilizable at high
temperature.

12. The method as claimed in claim 11, wherein the binder is a pressure
sensitive adhesive.

13. The method as claimed in claim 9, wherein step (d) further comprises
substeps of:(d1) disposing the preform in a container and between two
boards of a hot pressing machine;(d2) evacuating the air in the container
and filling a protective gas into the container;(d3) applying a pressure
on the preform through the two boards at a temperature for a period of
time; and(d4) relieving the pressure and cooling the preform to room
temperature to achieve the magnesium-based composite material.

14. The method as claimed in claim 13, wherein the pressure is in the
approximate range from 50 to 100 mega pascal, and the temperature is in
the approximate range from 300.degree. C. to 400.degree. C.

15. The method as claimed in claim 9, further comprising a step (f) of
annealing the magnesium-based composite material.

Description:

RELATED APPLICATIONS

[0001]This application is related to commonly-assigned application
entitled, "MAGNESIUM-BASED COMPOSITE MATERIAL AND METHOD FOR MAKING THE
SAME", filed **** (Atty. Docket No. US14243). Disclosure of the
above-identified application is incorporated herein by reference.

BACKGROUND

[0002]1. Field of the Invention

[0003]The present invention relates to composite materials and methods for
fabricating the same and, particularly, to a magnesium-based composite
material and a method for fabricating the same.

[0004]2. Discussion of Related Art

[0005]Nowadays, various alloys have been developed for special
applications. Among these alloys, magnesium alloys have relatively
superior mechanical properties, such as low density, good wear
resistance, and high elastic modulus. Generally, two kinds of magnesium
alloys have been developed: casting magnesium alloy and wrought magnesium
alloy. In wrought magnesium alloy, by using an extrusion process, most of
the casting defects can be eliminated and the metal grains can be
refined. However, the toughness and the strength of the magnesium alloys
are not able to meet the increasing needs of the automotive and aerospace
industry for tougher and stronger alloys.

[0006]To address the above-described problems, magnesium-based composite
materials have been developed. In the magnesium-based composite material,
nanoscale reinforcements are mixed with the magnesium metal or alloy. The
most common methods for making the magnesium-based composite material are
through powder metallurgy and stir casting. However, in powder
metallurgy, the metal or alloy is easily oxidized because the metal or
alloy is in the form of a fine powder. In particular, the magnesium
powder may spontaneously combust due to oxidization. In stir casting, the
nanoscale reinforcements are added to melted metal or alloy and are prone
to aggregate. As such, the nanoscale reinforcements can't be well
dispersed. Further, the above-mentioned methods generally include complex
processes using high cost manufacturing equipment.

[0007]What is needed, therefore, is to provide a magnesium-based composite
material and a method for fabricating the same, in which the above
problems are eliminated or at least alleviated.

SUMMARY

[0008]In one embodiment, a magnesium-based composite material includes at
least two magnesium-based metallic layers; and at least one
magnesium-based composite layer sandwiched by the at least two
magnesium-based metallic layers.

[0009]In another embodiment, a method for fabricating the above-mentioned
magnesium-based composite material, the method includes the steps of: (a)
providing at least two magnesium-based plates; (b) providing a plurality
of nanoscale reinforcements; (c) sandwiching the nanoscale reinforcements
between the at least two magnesium-based plates to form a preform; and
(d) hot pressing the preform to achieve the magnesium-based composite
material.

[0010]Other advantages and novel features of the present magnesium-based
composite material and the related method for fabricating the same will
become more apparent from the following detailed description of preferred
embodiments when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]Many aspects of the present magnesium-based composite material and
the related method for fabricating the same can be better understood with
reference to the following drawings. The components in the drawings are
not necessarily to scale, the emphasis instead being placed upon clearly
illustrating the principles of the present magnesium-based composite
material and the related method for fabricating the same.

[0012]FIG. 1 is a flow chart of a method for fabricating a magnesium-based
composite material, in accordance with a present embodiment;

[0013]FIG. 2 is a schematic view of a preform of the magnesium-based
composite material of FIG. 1;

[0014]FIG. 3 is a schematic view of a hot-pressing step of the method of
FIG. 1;

[0015]FIG. 4 is a schematic view of a magnesium-based composite material,
in accordance with a first embodiment; and

[0016]FIG. 5 is a schematic view of a magnesium-based composite material,
in accordance with a second embodiment.

[0017]Corresponding reference characters indicate corresponding parts
throughout the several views. The exemplifications set out herein
illustrate at least one preferred embodiment of the present
magnesium-based composite material and the related method for fabricating
the same, in at least one form, and such exemplifications are not to be
construed as limiting the scope of the invention in any manner.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0018]Reference will now be made to the drawings to describe, in detail,
embodiments of the present magnesium-based composite material and the
related method for fabricating the same.

[0019]Referring to FIG. 1, a method for fabricating a magnesium-based
composite material includes the steps of: (a) providing at least two
magnesium-based plates; (b) providing a plurality of nanoscale
reinforcements; (c) sandwiching the nanoscale reinforcements between the
at least two magnesium-based plates to form a preform; and (d) hot
pressing the preform to achieve the magnesium-based composite material.

[0020]In step (a), the material of the magnesium-based plates can,
beneficially, be pure magnesium or magnesium-based alloys. The components
of the magnesium-based alloys include magnesium and other elements
selected from a group consisting of zinc (Zn), manganese (Mn), aluminum
(Al), thorium (Th), lithium (Li), silver, calcium (Ca), and any
combination thereof. A weight ratio of the magnesium to the other
elements can advantageously, be more than about 4:1. The components of
the at least two magnesium-based plates can be the same or different. A
thickness of the magnesium-based plates can, beneficially, be in the
approximate range from 0.1 millimeter to 1 millimeter. Quite suitably,
the thickness of the magnesium-based plates is about 0.3 millimeter.

[0021]In step (b), the material of the nanoscale reinforcements can,
suitably, be selected from a group consisting of carbon nanotubes, carbon
nanofibers, silicon carbide nano-particles, alumina (Al2O3)
nano-particles, titanium carbide (TiC) nano-particles, and any
combination thereof. The diameter of the nanoscale reinforcements can,
beneficially, be in the approximate range from 1 nanometer to 100
nanometers. In the present embodiment, the diameter of the nanoscale
reinforcements is about 10 nanometers to 50 nanometers. The mass
percentage of the nanoscale reinforcements in the magnesium-based
composite material is in the approximate range from 0.5% to 2%. Quite
usefully, the weight percentage of the nanoscale reinforcement is 1%. It
is to be understood that the nanoscale reinforcements are not restricted
to the above-mentioned materials but any nanoscale particles having
reinforcement ability.

[0022]In the present embodiment, the nanoscale reinforcements is the
carbon nanotubes, and can, beneficially, be provided by a conventional
chemical vapor deposition (CVD) method.

[0023]In step (c), in the present embodiment, the nanoscale reinforcements
can, beneficially, be sandwiched by the at least two magnesium-based
plates by uniformly disposing the nanoscale reinforcements between the
two magnesium-based plates by the substeps of: (c1) forming a binder film
on a surface of one of the magnesium-based plates; (c2) uniformly
sprinkling the nanoscale reinforcements on the binder film; and (c3)
covering the nanoscale reinforcements by the other one of magnesium-based
plates to achieve the preform.

[0024]In step (c1), the material of the binder film is adhesive at room
temperature and volatilizable at high temperature. In the present
embodiment, the binder can, advantageously, be a pressure sensitive
adhesive.

[0025]It is to be understood that the nanoscale reinforcements can be
uniformly disposed between the two magnesium-based plates by any known
method in the art. In another embodiment, the nanoscale reinforcements
can be dispersed in a solvent and sprayed on the surface of one
magnesium-based plate and covered by the other magnesium-based plate. The
solvent is volatilizable at high temperature.

[0026]Referring to FIG. 2, a preform 100 formed in step (c), in the
present embodiment, includes two magnesium-based plates 110, a binder
film 120, and a plurality of nanoscale reinforcements 130. The binder
film 120 is formed on one magnesium-based plates 110. The nanoscale
reinforcements 130 are uniformly sprinkled on the binder film 120 and
sandwiched by the two magnesium-based plates 110. It will be apparent to
those having ordinary skill in the field of the present invention that
the number of the magnesium-based plates is arbitrary or depended on
actual needs/use. The nanoscale reinforcements are respectively
sandwiched by the magnesium-based plates.

[0027]Referring to FIG. 3, a hot-pressing machine 200 includes a container
220, and two boards 210 disposed in the container 220. The boards 210
can, beneficially, be heated to a predetermined temperature. A vacuum
pump (not shown in FIG. 2) can, usefully, be connected to the container
220 to evacuate the air therein. A protective gas can, suitably, be
filled into the container 230 through a pipe (not shown in FIG. 2)
connected thereto. The protective gas can, opportunely, be nitrogen
(N2) and/or a noble gas.

[0028]In step (d), the preform 100 can, advantageously, be hot pressed by
the hot-pressing machine 200 by the substeps of: (d1) disposing the
preform 100 between the two boards 210; (d2) evacuating the air in the
container 220 and filling a protective gas into the container 220; (d3)
applying a pressure on the preform 100 through the two boards 210 at an
elevated temperature for a period of time (e.g. about 5 to 15 hours); and
(d4) relieving the pressure on the preform 100 and cooling the preform
100 to room temperature to achieve the magnesium-based composite
material. Through hot pressing, the magnesium-based material infiltrates
into the interspaces between the nanoscale reinforcements and forms a
composite material. The pressure can, suitably, be in the approximate
range from 50 to 100 Mega Pascal (MPa). The temperature can, opportunely,
be in the approximate range from 300° C. to 400° C.

[0029]Quite suitably, an additional step (e) of annealing the
magnesium-based composite material can, advantageously, be further
provided after step (d). In step (e), the magnesium-based composite
material can be annealed in vacuum or in a protective gas. The protective
gas can, beneficially, be nitrogen (N2) and/or a noble gas. The
annealing temperature is in the approximate range from 180° C. to
320° C. The annealing time is about 2 to 3 hours. The annealing
step can eliminate defects in the magnesium-based composite material
caused by stress in step (d).

[0030]It is to be understood that, in the present method, the nanoscale
reinforcements are easier to be uniformly distributed in the composite
material than in the conventional methods (e.g. a stir casting method).
As such, the method can be easily used in mass production.

[0031]Referring to FIG. 4, the magnesium-based composite material 300 in
the first embodiment includes two magnesium-based metallic layers 310,
and one magnesium-based composite layer 320. The magnesium-based
composite layer 320 is sandwiched by the two magnesium-based metallic
layers 310 with a plurality of nanoscale reinforcements uniformly
dispersed therein. The thickness of the magnesium-based metallic layer
310 is in the approximate range from 0.2 to 0.4 millimeter. The thickness
of the magnesium-based composite layer 320 is in the approximate range
from 1 nanometer to 100 nanometers. In the magnesium-based composite
layer 320, magnesium-based metallic material is filled in the interspaces
between the nanoscale reinforcements, and thereby, forms a composite
layer. The nanoscale reinforcements uniformly dispersed in the
magnesium-based composite material. Therefore, the toughness and the
strength of the magnesium-based composite material can be enhanced.

[0032]Referring to FIG. 5, the magnesium-based composite material 400 in
the second embodiment is similar to the magnesium-based composite
material 300 in the first embodiment, and includes five magnesium-based
metallic layers 410, and two magnesium-based composite layers 420. The
two magnesium-based composite layers 420 are respectively sandwiched by
the five magnesium-based metallic layers 410.

[0033]It will be apparent to those having ordinary skill in the field of
the present invention that the number of the magnesium-based metallic
layers, and the magnesium-based composite layers is arbitrary or depended
on actual needs/use. The magnesium-based composite layers are
respectively sandwiched by the magnesium-based metallic layers. As the
number of the magnesium-based composite layers increased, the strength
and toughness of the magnesium-based composite material can be enhanced.

[0034]Finally, it is to be understood that the above-described embodiments
are intended to illustrate rather than limit the invention. Variations
may be made to the embodiments without departing from the spirit of the
invention as claimed. The above-described embodiments illustrate the
scope of the invention but do not restrict the scope of the invention.